Aluminum corrosion inhibitor

ABSTRACT

An aluminum corrosion inhibitor for use with -aqueous acids. The inhibitor may take the form of -a mixture of an anionic surface active agent and -one or more acetylenic compounds, which mixture -may further contain one or more of the following -materials: nitrogen base compounds, non-acetylenic -alcohols and aldehydes.

O United States Patent [1 1 [111 Keeney Apr. 9, 1974 ALUMINUM CORROSION INHIBITOR 3.319.714 5/1967 Knox 252/8.55 x Inventor: Billy R- y, Duncan, Okla- 3.382.l79 5/l968 Keeney et al. 252/396 X [73] Assignee: Halliburton Company, Duncan,

Okla Primary E.\'mninerHarry Wong, Jr. [22] Filed, June 16, 1971 Attorney, Agent, or Firm-Thomas R. Weaver; John H. Tregoning 21 Appl. No.: 153,841

Related U.S. Application Data [63] Continuation of Ser, No. 783,117. Dec. ll, 1968,

abandoned. [57] ABSTRACT [52] US. Cl 106/14, 252/146, 252/148,

252M515 252/388, 252/390 252/395 An alummum corrosion inhibitor for use wlth aqueous [51 Int. Cl C09d 5/08 acids' The inhibitor may take the form of a mixture of [58] Field of Search 106/14- 252/79. 1, 79.2, Surface active agent and ("more acet- 252/79 4 389 390, 396 ylenic compounds, which mixture may further contain one or more of the following materials: nitrogen base [56] References Cited compounds, non-acetylenic alcohols and aldehydes.

UNlTED STATES PATENTS 3,404,094 10/1968 Keeney 252/396 X 18 Claims, N0 Drawings ALUMINUM CORROSION INHIBITOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to corrosion inhibitors and methods for inhibiting the corrosion of metals, and more particularly, but not by way of limitation, to an aluminum corrosion inhibitor for use with aqueous acids, and to methods for inhibiting the corrosion of aluminum by aqueous acids.

2. Description of the Prior Art Prior known compositions for the inhibition of corrosion of aluminum surfaces when contacted with aqueous acids have been employed with varying degrees of success. A failing of these prior art corrosion inhibiting compositions is that they cease to be effective after relatively short periods of time or breakdown under high temperature conditions, that is, temperatures in the range of from 125 to 175F., or higher. A further failing of these prior art compositions is that they are not effective to a comparable degree for substantially all commonly used aluminum alloys.

SUMMARY OF THE INVENTION The present invention relates to new and useful compositions which may be employed in acid solutions to decrease or inhibit the corrosion of aluminum in contact with the acid solutions. The present invention provides a corrosion inhibitor for inhibiting the corrosion of aluminum and alloys thereof by aqueous acids, which inhibitor comprises an anionic surface active agent and an acetylenic compound. The invention further provides a method for inhibiting the corrosion of aluminum and alloys thereof.

The present invention is particularly useful in cleaning aluminum with aqueous acids such as in the removal of scale from aluminum heat exchangers, tanks, pipes, etc., with dilute hydrochloric acid and inhibiting corrosion of aluminum tanks, pipes, etc., which must contain dilute acids.

It is therefore an object of the present invention to provide an inhibitor composition and a method of inhibiting corrosion of aluminum surfaces when such surfaces are contacted by aqueous acids.

Another object of the present invention is the provision of an inhibitor composition and a method ofinhibiting the corrosion of aluminum surfaces when contacted with aqueous acids, which composition and method are effective at low temperatures as well as high temperatures.

A further object of the present invention is to provide an inhibitor composition and a method of inhibiting the corrosion of aluminum and alloys thereof when contacted with acid solutions, especially hydrochloric acid at high temperatures for relatively long periods of time.

Yet a further object of the present invention is to provide an inhibitor composition and a method of inhibiting aluminum and alloys thereof when contacted with acid solutions whereby a comparable degree of corrosion inhibition may be obtained for most commonly used aluminum alloys.

These and other objects and advantages of the present invention will become readily apparent from the description of the invention and examples which follow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been discovered that an anionic surface active agent and an acetylenic compound, in particular amounts of each, provides a composition having superior aluminum corrosion inhibiting properties when added in proper order in small quantities to an acid solution constituting the corrodent. In addition, an anionic surface active agent together with a synergistic blend of an acetylenic compound and a non-acetylenic alcohol; or one or more acetylenic compounds, a nitrogen base compound and one or more non-acetylenic alcohols; or one or more acetylenic compounds, a nitrogen base compound and an aldehyde or a solution of aldehyde in alcohol; when added to a corrodent acid solution in particular quantities and in particular order provide compositions having superior aluminum corrosion inhibiting properties. The relative amounts of the acetylenic compound, non-acetylenic alcohol, nitrogen base compound and aldehyde may vary over a wide range. Furthermore, it has been found that one of the preferred compositions described above may be used in preference to another to obtain the best corrosion inhibiting properties, depending on the particular aluminum alloy to be protected, the temperatures to be encountered, and the strength or concentration of the acid corrodent. In general, the anionic surface active agent concentration in the corrosion inhibitor may vary from about 15% to 35%. However, lower and higher concentrations will still be effective.

In the preferred form of the invention the anionic surface active agent is a saturated hydrocarbon sulfonate having the general formula RSO X with R being a C to C saturated hydrocarbon chain and X being an alkali metal or ammonium. The sulfonate is made by treating a saturated hydrocarbon (aliphatic or cycloali phatic) of some predetermined chain length with sulfur dioxide and chlorine in the presence of actinic light. Gamma radiation and certain catalysts can be substituted for the actinic light. This forms a hydrocarbon sulfonyl chloride which is subsequently neutralized with an alkali metal hydroxide or ammonium hydroxide. The preferred material has the formula C H SO Na and is made by gassing a C- 13 straight chain saturated hydrocarbon (aliphatic) to a specific gravity of 0.91 to 0.97 before neutralization. The anionic surface active agent C,,-,H SO Na is sometimes referred to herein after as CRA. US. Pat. No. 2,999,812 illustrates a method of preparing this preferred surface active agent.

Some examples of other anionic surface active agents which may be employed in the present invention are alkyl taurate, alkyl phosphate, alkyl sulfate, alkyl sulfonate, and alkyl aryl sulfonate.

In the preferred form of the invention, acetylenic alcohols having an ethynyl hydrogen on the acetylenic group are employed as the acetylenic compound component. Some examples of acetylenic alcohols or compounds which may be employed in the present invention are: hexynol, dimethylhexynol, dimethylhexynediol, dimethyloctynediol, methylbutynol, methylpentyno], ethynyl cyclohexanol, 2-ethylhexanol, phenylbutynol, and ditertiary acetylenic glycol. Other acetylenic compounds which can be employed in accordance with the present invention are for example, butynediol, l-ethynylcyclohexanol, 3-methyll -nonyn- 3-ol, 2-methyl-3-butyn-2-ol, also l-propyn-3-ol, lbutyn-3-ol, l-pentyn-3-ol, l-heptyn-3-ol, l-octyn-3-ol, l-nonyn-3-ol, l-decyn-3-ol, l-(2, 4, 6-trimethyl-3- cyclohexenyl) -3-propyne-l-ol, and in general acetylenic compounds having the general formula wherein R is an alkyl, phenyl, substituted phenyl or hydroxyalkyl radical or H, and the alpha R's may be joined together to form a cyclohexyl ring.

Acetylenic sulfides having the general formula HC E C-RS-RC CH can also be employed in the present invention in lieu of the acetylenic alcohols. Examples of these are diproparagyl sulfide, bis (l-methyl-2-propynyl) sulfide and his (2-ethynyl-2-propyl) sulfide.

The non-acetylenic alcohols suitable for use in the present invention have the general formula ROH, wherein R is either an alkyl group or a ketone group. Some examples of these alcohols are diacetone alcohol, normal propanol, isopropanol, ethanol, methanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, and I-S-pentanediol.

The nitrogen or ammonia base compounds that may be employed in accordance with the present invention are those amines such as mono-. diand trialkyl amines having from two to six carbon atoms in each alkyl moiety, as well as the six-membered n-heterocyclic amines, for example alkyl pyridines and mixtures thereof. These compounds include such amines as ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, mono-, di-, and tributylamine, mono-, di-, and tripentylamine, mono-, di-, and trihexylamine, and isomers of these, such as isopropylamine, tertiary butylamine, etc. The suitable nitrogen compounds also include alkyl pyridines having from one to five nuclear alkyl substituents per pyridine moiety, with such alkyl substituents having from one to 12 carbon atoms. The pyridines are preferred which have an average of six carbon atoms per pyridine moiety, e.g., a mixture of high boiling tertiary-nitrogen-heterocyclic compounds such as HAP (high alkyl pyridines), Reilly -20 base and alkyl pyridines H8.

The aldehydes which may be used in accordance with the present invention include alkyl aldehydes, aryl aldehydes, alkylaryl aldehydes. The aldehydes may be substituted with non-deleterious substituents, such as hydroxyl group, and may be saturated or unsaturated. Suitable aldehydes include formaldehyde, benzaldehyde, butyraldehyde, B-hydroxybutyraldehyde (aldol) propionaldehyde and glyoxal. The aldehyde may be used alone or in a suitable solvent such as alcohol.

Anionic surface active agents of this invention are generally not compatible with the other compounds employed in the corrosion inhibiting composition. Therefore, the corrosion inhibitor composition should be made up in two parts, the first part composed of the anionic surface active agent, and the second part composed of the acetylenic compound, or a blend of the acetylenic compound and the other compounds disclosed above. The acid solution containing the corrosion inhibitor composition may then be prepared by preparing the desired acid solution, then combining the surface active agent with the acid solution and mixing it thoroughly, and then combining the acetylenic compound or blend of acetylenic compound and other compounds with the acid solution and mixing thoroughly. Another method for preparing an acid solution containing the corrosion inhibitor composition of the present invention is to combine the surface active agent with a proper amount of water stirring it thoroughly, then combining the acetylenic compound or blend of acetylenic compound and other compounds with the water and stirring it thoroughly, and thereafter combining a proper amount of acid to complete the desired acid solution.

On a basis of a volume of 100 per cent, a preferred composition of the present invention is comprised as follows:

Per Cent Anionic Surface Active Agent 15-35 Acetylenic Compound -85 Another preferred composition of the present invention is comprised as follows:

Per Cent Anionic Surface Active Agent 15-35 Acetylenic Compound 30-60 Nitrogen Compound 0-8 lO-SO Non-acetylenic Alcohol Yet another preferred composition of the present invention is comprised as follows:

Per Cent Anionic Surface Active Agent 15-35 Acetylenic Compound 30-60 Nitrogen Compound 0-8 Aldehyde 10-30 Non-acetylenic alcohol 5-15 Composition A Compound Parts by Per Cent Volume By Volume CRA 1.0 30.0 Ethyl Octynol 2.33 70.0

Another preferred specific composition, sometimes referred to herein as composition B is as follows:

Composition B Compound Parts by Per Cent Volume By Volume CRA 1.0 30.0

Composition B Compound Parts by Per Cent Volume By Volume Ethyl Octynol 1.6 49.0 Diacetone Alcohol 0.7 21.0

Yet another preferred composition, sometimes referred to herein as composition C is as follows:

Composition C Compound Parts by Per Cent Volume By Volume CRA 1.00 25.0 Propargyl Alcohol 1.38 34.4 Ethyl Octynol 0.14 3.4 Alkyl Pyridines l-lB 0.11 2.8 Diacetone Alcohol 138 34.4

Still another preferred composition, sometimes referred to herein as Composition D is as follows:

Composition D A further preferred composition of the present invention, sometimes referred to herein as composition E is as follows:

Composition E Compound Parts by Per Cent Volume By Volume CRA 1.00 25.0 Propargyl Alcohol 1.38 34.4 Ethyl Octynol 0.14 3.4 Alkyl Pyridines HB 0.11 2.8 Diacetone Alcohol 0.41 10.3 Normal Propanol 0.96 24.1

A number of laboratory tests were conducted wherein the preferred blends of this invention, compositions A, B. C, D, and E, were tested at various temperatures, in various amounts with various aluminum alloys, under static conditions and dynamic conditions, in various hydrochloric acid solutions.

PROCEDURE FOR STATIC TESTS ln these tests, the acid solutions were mixed by diluting Be l-lCL with water to the desired concentrations. A portion of each acid solution was then titrated with a standard base solution to ascertain the exact acid concentration. The various acid solutions were prepared in advance in sufficient quantities to complete an entire series of tests with the same batch of acid. Corrosion coupons of various types of aluminum were ordered in sufficient quantities to complete a series of tests on the same batch of coupons. The coupons were cleaned as follows: Scrubbed by hand with a fine nylon brush in a detergent containing a pumice, rinsed, dipped in acetone to remove the access water and then dipped in alcohol and allowed to dry. They were then weighed to the nearest milligram and stored in a desiccator until time for use.

Tests were conducted at various temperatures.

The acid solution was poured into glass bottles in sufficient quantity to approximate the specific acid volume to coupon surface area ratio that was desired. The quantity of acid used was dependent upon the surface area of the coupon to be tested. In most of the static tests, a 25 cc./in. acid volume to coupon surface area ratio was used. After the desired amount of acid was poured into the bottles, the inhibitor composition was added with a hypodermic syringe, with the anionic surface active agent being added first separately and stirred with a glass rod, and then the other compounds in the particular inhibitor composition tested added and stirred with a glass rod. The inhibited acid solution was then placed in a water bath which had been set at a predetermined temperature and allowed to pre-heat for 20 minutes. After this time, the coupons were placed in the preheated inhibited acid solutions. The coupons were left in the acid solutions for the specified test time, then removed, neutralized, recleaned, rinsed, dipped in acetone and then alcohol, allowed to dry, and then reweighed.

PROCEDURE FOR DYNAMIC TESTS The acid solutions in these tests were mixed and titrated in the same manner as outlined above for the static tests. In these tests 1 inch OD aluminum alloy tubing was cut into test specimens each measuring 6 inches. The specimens were cleaned by scrubbing by hand with a fine Nylon brush and a detergent containing pumice, rinsed, clipped in acetone to remove the excess water, and then placed in a desiccator and allowed to come to room temperature. The specimens were then weighed to the nearest milligram and stored in a desiccator until time for use.

The scaled specimens which had been pro-weighed to the nearest milligram were prepared by stopping up one end of the specimen and filling the specimen with a scaling solution. The scaling solution was calcium bicarbonate solution prepared by reacting a ten per cent calcium chloride solution with a sixteen per cent ammonium bicarbonate solution. The specimens containing the sealing solutions were then placed in an oven set at a temperature of 200F. The scaling solution was allowed to evaporate leaving a calcium carbonate scale on the test specimens. The scaled specimens were then re-weighed to the nearest milligram and stored in a desiccator until time for use. All of these tests were conducted in a closed acid circulating system which had been calibrated to a desired velocity of acid flow.

The acid solution was poured into a glass bottle in sufficient quantity to approximate the specific acid volume-to-specimen surface area ratio that was desired. In most of these tests a 123 cc./in. volume to specimen surface area ratio was used. After the desired amount of acid was poured into the bottles, the inhibitor was added with a hypodermic syringe, the anionic surface active agent being combined first and stirred with a glass rod, and then the other compounds in the composition tested were combined and stirred.

The flow rate of the system was calibrated by using a flow meter to measure flow and a variable resistor to regulate the speed of a circulating pump. The temperature of the acid solution was maintained at the desired temperature for each test by use of a hot plate which was controlled with a Tole-Thermometer. The speci- From the above Table it can be seen that best results were obtained with CRA in composition D.

TABLE I1 COMPARISON OF VARIOUS ACETYLENIC ALCOHOLS AND C H SO Nu (CRA) MIXTL'RFS WITH COMPOSITION A Composition A mens were exposed to the circulating acid solution for the specified time, then removed, neutralized, cleaned, rinsed, dipped in acetone, allowed to dry, and then reweighed.

in both the static tests and dynamic tests the loss in weight of the coupons and/or specimens was multiplied times a calculated factor to convert the loss in weight to lbs./ft. /24 hrs. The factor was calculated as follows:

2 ft. =factor 454 Surface Area of fi'specimen-in."

I 1 day X Test T1me-h.rs. 24 hm Example: Test time, 6 hours, surface area of coupon 4.0 in. then 144/454 X 4.0 X (6/24) 0.317 lb./ft. /day The results of these tests are set forth below:

TABLE I COMPARISON OF VARIOUS ANIONIC SURFACE ACTIVE AGENTS Type of Test Static Test Temperature 125F. Test Time 4 hrs. Metal Type Aluminum Alloy-3003 Corrodent 5% HCI Pressure Atmospheric Acid Volume-Surface Area Ratio: cc./ln.

inhibitor Volume Per Cent Corrosion Concentration Rate in Lbs/Ft.

of inhibitor /day None None 0.775 CRA 0.1 0.368 Composition D .4 0.004 Alkyl Taurate 0.1 0.097 Alkyl Phosphate 0.1 0.124 Alkyl Sulfate 0 1 0.136 Composition D w/ Alkyl Taurute in lieu of CRA 0.4 0.025 Composition D w/ Alkyl Phosphate in lieu of CRA 0.4 0.072 Composition D w/ Alkyl sulfate in lieu of CRA 0.4 0.008

As can be seen from the above data Composition A achieved the best result but relatively good results were also achieved with the other acetylenic alcohols tested.

TABLE III INHIBITOR COMPOSITION B-CORROSION RATES FOR VARIOUS ACID STRENGTHS AND TEMPERATURE Two specimens were subjected to the scaling process described above for the purpose of determining the amount of corrosion caused by sealing alone. After the scale was laid down on two specimens it was removed by brushing the specimens with a soft brush in warm water. The specimens were weighed before scaling and after the scale had been removed in order to determine weight loss due to the scale. Table IV shows the results of these tests.

Corrosion tests were conducted with inhibitor composition B in 5 per cent, 7% per cent and 10 per cent hydrochloric acid solutions at F. on specimens that contained a calcium carbonate scale layed down on the specimens as described above. These tests were conducted to determine if the inhibitor system would protect the aluminum surface once the scale had been removed by the acid. Table V reflects the results of these tests. The corrosion rates reported in this table have been corrected to reflect only the amount of corrosion that occurred from the acid solutions. The average weight loss from the scaling process reflected in Table IV was deducted from the weight loss obtained with sealed specimens contacted by the acid solutions so that the reported corrosion rates in Table V reflect only the corrosion resulting from the inhibited acid solutrons.

TABLE IV CORROSION OF SPECIMENS DUE TO SCALING Metal Type Aluminum AIIoy-3003I-II4 Original Final Wt. Average Wt. Specimen Wt. in Wt. in Loss In Loss In Grams Grams Grams Grams No I 51800 5I.79l 0.009 No 51.757 5l.750 0.007 0.008

TABLE V INHIBITOR COMPOSITION B CORROSION OF SCALED SPECIMENS Type of Test Dynamic Test Temp. I50F. Test 'I ime 6 hours Metal Type Aluminum Alloy-3003 H14 containing a CaCO: Sculc Acid Velocity I fL/see. Pressure Atmospheric Acid Volume-Surface Area Ratio: I23 cc./in.

Volume Per Cent Concentration Corrodent Weight of Corrosion Rate of (Volume CuCO Scale in Lbs/Ft. Composition B Per Cent) in Grams /Day L HCI 5.896 0.0037 l.0 7V271 HCI 5.695 0.0064 I0 I07: HCI 5.821 0.0095

As can be seen by comparing Table III with Table IV very little additional corrosion took place as a result of the calcium carbonate scale, and the inhibitor system was very effective in protecting the aluminum specimen surface once the scale had been removed by the corrodent.

TABLE VI INHIBITOR COMPOSITION C- CORROSION RATES FOR VARIOUS ALUMINUM ALLOYS AA-20I7 None 2.840

AA-20l7 0.4 0.004

AA-2024 None 1.145

AA-2I 17 None 3.12l

AA-2l 17 0.4 0.005

AA-3003 None 0.775

AA-3003 0.4 0.00l

AA-4043 None 2.870 AA-4043 0.4 0.006

AA-5005 None 0.298 AA-SOOS 0.4 0.000

AA-5052 None 0.608 AA-5052 0.4 0.00l

AA-5056 None 1.300

AA-6053 None 0.094

AA-606l None 1.323

AA-606I 0.4 0.000

AA-6063 None 0.626

TABLE VII INHIBITOR COMPOSITION D-CORROSION RATES FOR VARIOUS ALUMINUM ALLOYS Type of Test Static Test Temp. F. Test Time 4 hours Corrodent 5% HCI Velocity 3.065 ft/sec. Pressure Atmospheric Acid Volume-Surface Area Ratio: 181 cc./in.

Volume Type of Per Cent Corrosion Aluminum Concentration Rate in Lbs.

of Composition D lFtF/Day AA-3003 None Completely Dissolved AA-3003 .55 0.015

AA-SOOS None 1.07 AA-SOOS .55 0.0008

AA-606l None Completely Dissolved AA-6061 .55 0.0I3

TABLE VIII INHIBITOR COMPOSITION E-CORROSION RATES FOR VARIOUS ALUMINUM ALLOYS BY VARIOUS ACID SOLUTIONS AT VARIOUS TEMPERATURES Type of Test Static Test Time 4 hours Pressure Atmospheric Acid Volume-Surface Area Ratio: 25 cc./in.

Volume PcrCent Corrodent Concentration Corrosion Type of Test (Volume of Rate in Lbs. Aluminum Temp. Per Cent) Composition E lft. 2/Duy AA-3003 l25F. 5'71 HCI 0.4 0.001

AA-SOOS I25F 5V1 HCI 0.4 0.00I

AA-3003 I2SF. 7.571 HCI 0.4 0.002

TABLE-VIII -Continued INHIBITOR COMPOSITION E-CORROSION RATES FOR VARIOUS ALL'MINLM ALLOYS BY VARIOUS ACID SOLL'TIONS AT VARIOUS TEMPERATURES Type of Test Static Test Time 4 hours Pressure Atmospheric Acid Volume-Surface Area Ratio 25 ccvin.

\olume Per Cent Corrodent Concentration Corrosion Type of Test (Volume of Rate in Lbs. Aluminum Temp Per Cent Composition E ft. Z/Du AA-SOOS I25F 7.5 r HCI 0.4 0.002

AAJOUB 12520 F. l71 HCI 0.4 0.002

AA-SOOS 125F. 10'71 HCI 0.4 0.002

AA-3003 [50F '71 HCI 0.4 0.001

AA'SOOS l5()F. 5'71 HCI 0.4 0.001

AA-3003 l50F 7.571 HCI 0.4 0.002

AA-SOOS ISOF. 7.57! HCI 0.4 0.002

AA-3003 150F. I07: HCI 0.4 0.002

AA-5005 I50F. l07r HCI 0.4 0.002

TABLE IX COMPARISON OF INHIBITOR COMPOSITIONS A AND B Type of Test Dynamic Test Temp. 150F. Test Time 6 hours Corrodent 5% HCI Metal Type AA-3003 Pressure Atmospheric Acid Volume-Surface Area Ratio: I23 cc/in.

Volume Per Cent Concentration of Inhibitor Composition Corrosion Rate in Lbs/FtlDay Inhibitor Composition As can be seen from the above data the particular composition of the present invention which should be used for a particular application to obtain the best protection depends on the aluminum alloy to be protected, the strength of the acid solution to be employed, and temperatures to be encountered.

TABLE X CORROSION RATES OF VARIOUS ACID SOLUTIONS WITH AND WITHOUT COMPOSITION D Type of Test Static Test Temp. 125F. Test Time 4 hours Metal Tested AA-3003 Aluminum Pressure Atmospheric Acid Volume-Surface Area Ratio: 25 cc/in.

Volume Per Cent Concentration Corrodent Corrosion Rate As can be seen from the above table Inhibitor Composition D afforded some protection to the aluminum samples tested when combined with the various acid solutions tested, with the exception of Formic Acid which is not very corrosive to aluminum without inhibition.

From the above it may be seen that the inhibitor or inhibitor compositions of the present invention are operable when employed at temperatures as high as F. in various acid concentrations. The corrosion which does occur is substantially uniform regardless of temperatures encountered and alloys protected. The corrosion inhibitor compositions provide long term protection at small concentrations and are particularly effective on aluminum and the various alloys thereof.

Applications in which the inhibitor of the present invention is particularly useful include cleaning of aluminum tanks, heat exchangers, pipe, etc., and preventing corrosion of aluminum tanks or vessels which must contain quantities of dilute acid.

The inhibitor of the present invention is preferably added to the acid in amounts by volume from about 0.05 per cent to 20 per cent. The amount of inhibitor required and the specific inhibitor composition will vary with the temperatures to be encountered, the particular aluminum alloy to be protected, and the strength or concentration of the acid solution used. The first part of the inhibitor, that is, the anionic surface active agent, should be combined first and mixed, and then the acetylenic compound, or mixture of acetylenic compound and non-acetylenic alcohol, or mixture of acetylenic compound, nitrogen compound, and nonacetylenic alcohol or mixture of acetylenic compound, nitrogen compound, and aldehyde, should be combined and mixed. The inhibitor composition may be added either to the water before acid is added or directly to the acid soltuion.

Broadly, the present invention relates to a new and improved corrosion inhibitor or composition for reducing the corrosive effect of aqueous acids on aluminum and the various alloys thereof consisting essentially of an anionic surface active agent and an acetylenic compound, or an anionic surface active agent and a synergistic blend of either an acetylenic compound and nonacetylenic alcohol or an acetylenic compound, a nitrogen or ammonia base compound and a non-acetylenic alcohol or aldehyde, in certain amounts of each.

What is claimed is:

1. A composition consisting essentially of:

an aqueous hydrochloric acid solution having in the range of about 0.5 to 15% hydrochloric acid by weight of said solution;

a surface active agent selected from compounds represented by the general formula R SO X and mixtures thereof, wherein R is a saturated hydrocarbon radical having in the range of about eight to 25 carbon atoms and X is an alkali metal or ammonium; and

an acetylenic compound selected from compounds represented by the general formula lenic compound is selected from the group consisting of ethyl octynol, propargyl alcohol, methyl butynol, hexynol, and mixtures thereof.

alkyl pyridines and normal propanol.

alcohol represented by the formula R OH wherein R is a radical selected from the group consisting of alkyls and ketones.

3. The composition of claim 2 further consisting of a 15 nitrogen base selected from the group consisting of mono-, di-, and trialkyl amines having from two to six carbon atoms in each alkyl moiety and 6-membered N- heterocyclic amines.

4. The composition of claim 1 wherein said surface active agent is represented by the chemical formula C H SO Na.

5. The composition of claim 4 wherein said acety- 6. The composition of claim 4 wherein said acetylenic compound is ethyl octynol.

diacetone alcohol.

8. The composition of claim 7 further consisting of formaldehyde.

9. The composition of claim 7 further consisting of 10. A method for protecting a metal selected from aluminum, aluminum alloys and mixtures thereof against corrosion by an aqueous hydrochloric acid solution in contact therewith, comprising contacting said metal with a composition consisting essentially of:

an aqueous hydrochloric acid solution having in the range of about 0.5 to 15% hydrochloric acid by weight of said solution;

a surface active agent selected from compounds represented by the general formula R,so x and mixtures thereof, wherein R is a saturated hydrocarbon radical having in the range of about eight to 25 carbon atoms and X is an alkali metal or ammonium; and

an acetylenic compound selected from compounds represented by the general formula I H-CEC-C-OH and mixtures thereof, wherein R and R are selected from alkyls and hydrogen and mixtures thereof; and further wherein said hydrochloric acid solution is present in the range of about 98 to about 99.6% by weight of said composition, said surface active agent is present in the range of about 0.06 to about 0.7% by weight of said composition, and said acetylenic compound is present in the range of about 0.26 to about 1.7% by weight of said composition.

11. The method of claim 10 wherein said composition further consists of an alcohol represented by the formula R Ol-I wherein R is a radical selected from the group consisting of alkyls and ketones.

12. The method of claim 11 wherein said composition further consists of a nitrogen base selected from the group consisting of mono-,-di-, and trialkyl amines having from two to six carbon atoms in each aklyl moiety and 6-membered N-heterocyclic amines.

13. The method of claim 10 wherein said surface active agent is represented by the chemical formula C13H27SO3Na.

14. The method of claim 13 wherein said acetylenic compound is selected from the group consisting of ethyl octynol, propargyl alcohol, methyl butynol, hexynol, and mixtures thereof.

15. The method of claim 13 wherein said acetylenic compound is ethyl octynol.

16. The method of claim 14 wherein said composition further consists of diacetone alcohol.

17. The method of claim 16 wherein said composition further consists of formaldehyde.

18. The method of claim 16 wherein said composition further consists of alkyl pyridines and normal propanol.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,802,890 Dated April 9, 1974 .Inventofls) Billy Keeney It is certified that error appears in the above-identified patent and-that said Letters Patent are hereby corrected as shown below:

In Column 6, line 47, delete the word "sealing" and insert therefor --scaling.

In Column 7, line 43, delete the line which reads 144/454 X 4.0 X (6/24) 0.317 lb./ft. /day" and insert In Column 7, Table I, the column entitled "Inhibitor" delete "Composition D w/ Alkyl sulfate lieu of CRA" and insert therefor --Composition D w/ Alkyl sulfate in lieu of CRA. In the Column entitled "Volume Per Cent Concentration of Inhibitor" delete the word "in" which is reflected for Composition D w/Alkyl sulfate in lieu of CRA.

' Signed and sealed this 17th day of September 1974.

(SEAL) Attes t:

McCOY M. GIBSON JR. 7 C. MARSHALL DANN Artestinz Officer Commissioner of Patents FORM F'O-lOSO (IO-69'! USCOMIWDC 603764369 0 u s oovzuumzm mmmm. OFFILE- I969 osss3a4.

Patent No. 3, 02, 90 Dated April 9, 1974 Inventor(s) l y -v- Keeney It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 6, line 47, delete the word "sealing" and insert therefor scaling.

In Column 7, line 43, delete the line which reads "144/454 X 4 .0 X (6/24) 0.317 lb./ft. /day" and insert In Column 7, Table I, the column entitled "Inhibitor" delete "Composition D w/ Alkyl sulfate lieuof CRA" and insert therefor Composition D w/ Alkyl sulfate in lieu of CRA-. In ,the Column entitled "Volume Per Cent Concentration of Inhibitor" delete the word "in" which is reflected for Composition D w/Alkyl sulfate in lieu of CRA.

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C MARSHALL DANN restin Officer Commissioner of Patents USCOMM-DC 60376-P69 n u s novsnmasm I'HINTINI. nrnct I969 0-36033A, 

2. The composition of claim 1 further consisting of an alcohol represented by the formula R4OH wherein R4 is a radical selected from the group consisting of alkyls and ketones.
 3. The composition of claim 2 further consisting of a nitrogen base selected from the group consisting of mono-, di-, and trialkyl amines having from two to six carbon atoms in each alkyl moiety and 6-membered N-heterocyclic amines.
 4. The composition of claim 1 wherein said surface active agent is represented by the chemical formula C13H27SO3Na.
 5. The composition of claim 4 wherein said acetylenic compound is selected from the group consisting of ethyl octynol, propargyl alcohol, methyl butynol, hexynol, and mixtures thereof.
 6. The composition of claim 4 wherein said acetylenic compound is ethyl octynol.
 7. The composition of claim 5 further consisting of diacetone alcohol.
 8. The composition of claim 7 further consisting of formaldehyde.
 9. The composition of claim 7 further consisting of alkyl pyridines and normal propanol.
 10. A method for protecting a metal selected from aluminum, aluminum alloys and mixtures thereof against corrosion by an aqueous hydrochloric acid solution in contact therewith, comprising contacting said metal with a composition consisting essentially of: an aqueous hydrochloric acid solution having in the range of about 0.5 to 15% hydrochloric acid by weight of saId solution; a surface active agent selected from compounds represented by the general formula R1SO3X and mixtures thereof, wherein R1 is a saturated hydrocarbon radical having in the range of about eight to 25 carbon atoms and X is an alkali metal or ammonium; and an acetylenic compound selected from compounds represented by the general formula
 11. The method of claim 10 wherein said composition further consists of an alcohol represented by the formula R4OH wherein R4 is a radical selected from the group consisting of alkyls and ketones.
 12. The method of claim 11 wherein said composition further consists of a nitrogen base selected from the group consisting of mono-, di-, and trialkyl amines having from two to six carbon atoms in each aklyl moiety and 6-membered N-heterocyclic amines.
 13. The method of claim 10 wherein said surface active agent is represented by the chemical formula C13H27SO3Na.
 14. The method of claim 13 wherein said acetylenic compound is selected from the group consisting of ethyl octynol, propargyl alcohol, methyl butynol, hexynol, and mixtures thereof.
 15. The method of claim 13 wherein said acetylenic compound is ethyl octynol.
 16. The method of claim 14 wherein said composition further consists of diacetone alcohol.
 17. The method of claim 16 wherein said composition further consists of formaldehyde.
 18. The method of claim 16 wherein said composition further consists of alkyl pyridines and normal propanol. 